Control switch for discharge lamps



Feb. 22, 1949. w, COOK 2,462,306

CONTROL SWITCH FOR DISCHARGE LAMPS Filed Sept. 17, 1945 Inventor- Leonarci W.C 00 k,

H i s Attorney;

Patented Feb. 22, 1949 CGN'ERGL SWITCH FOR DISCHARGE LAMPS Leonard W.Cook, Stratford, Conn., assignor to General Electric Company, acorporation of New York Application September 17, 1945, Serial No.616,907

6 Claims.

My invention relates to a control switch for starting and operatinggaseous electric discharge lamps and more particularly to a startingswitch for fluorescent lamps used in commercial and residence lightingsystems.

In such lighting systems the discharge lamps are connected in serieswith a ballast across a source of electric power together with astarting switch in parallel with the lamp but in series with the lampelectrodes. When the control switch opens the circuit between theelectrodes, the ballast applies a high voltage kick to start the lamp.Such control switches are known to the trade as starters.

Such starters as presently designed. provide for an appreciablepreheating time for the filamentary electrodes of the lamp to bring themup to an emissive temperature before applying the high voltage from theballast to start the lamp. However, with certain types of fluorescentlamps now on the market, appreciable preheating of the electrodes isunnecessary. The lamp may be started without any substantial preheat ofthe electrodes or with cold cathodes.

Although present day lamps are designed for instant starting withlittle, if any, preheating of the electrodes, or for cold cathodestarting, starters of the type now commercially available will not starta lamp fast enough to avoid a noticeable delay in lighting after thepower supply switch is closed and, in any event, do not start a lampwith the speed at which the lamp is capable of being started.

One such type of starter now on the market employs a glow switch havingtwo electrodes one of which is bimetallic. When the lamp operatingcircuit is closed, a glow discharge takes place between the electrodesto heat the bimetallic electrode to close the circuit through the glowswitch. This extinguishes the glow discharge and causes a preheatcurrent to flow through the lamp filaments. When the bimetallic membercools down, the circuit through the glow switch is opened causing theballast to apply a high voltage across the filaments to start the lamp.Although this starter operates satisfactorily when it is desired topreheat the lamp electrodes, it fails to provide an instant startingaction for lamps of the type now commercially available in which noappreciable preheating of the electrodes is required and which may, infact, be started with cold cathodes.

When thermal-type starting switches are employed, an unavoidable timedelay is encounteredin heating and cooling the relatively heavybimetallic strips. When glow switches alone are emplcyed, an appreciabledelay occurs after extinguishment of the glow discharge waiting for thebimetallic element to cool down.

A magnetic vibrator type of starter has been used in certain instancesand which opens the circuit across the lamp filaments almost instantlyafter closure of the .power switch. However, in such circuits, theactuating element of the magnetic coil of the switch is continuously inthe lamp circuit during operation of the lamp to maintain the contactsin open position with consequent loss of power. This objection has beenovercome to some extent by employing a voltage responsive device such asa glow lamp in series with the magnet coil, the two being in parallelwith magnetically operated contacts. The glow lamp cuts ofi the magneticswitch from the power supply during operation of the lamp. Such anarrangement is disclosed in Patent 2,212,427 issued on August 20, 1940to Leo R. Peters and assigned to the same assignee as the instantapplication.

While for certain applications, the circuit of the Peters patentoperates satisfactorily, it has been found that part of the voltageobtained across the vibrator contacts is absorbed in the glow lamp andcoil and hence is not available across the lamp electrodes.

The disadvantages of the aforementioned starters are overcome by my newand improved starter. It employs a glow discharge device and magneticswitch in series between the lamp electrodes. It operates extremely fastto supply high voltage from the ballast to give a practicallyinstantaneous start of the lamp after closure of the power supplyswitch. After the lamp starts, the starter is blocked out of the circuitso that it consumes no current. In'certain applications, the starter maybe provided with a lock-out mechanism which will cut the starter out ofthe lamp operating circuit if the lamp fails to start after apredetermined number of attempts.

Therefore, one object of my invention is to provide a new andimprovedstarter for electric discharge lamps, which will start the lamps almostinstantaneously.

Another object of my invention is to provide an improved starter whichincludes means for starting the lamp instantaneously, in combinationwith a mechanism for locking the starter out of the lamp operatingcircuit in the event that the lamp fails to light after several startingattempts.

In the accompanying drawing, Fig. 1 is a schematic view showing astarter constructed in accordance with my invention and connected into alamp operating circuit; and Fig. 2 is a view 3 of the starter similar toFig. 1 but with the addition of a lock-out mechanism.

Referring to Fig. 1 of the drawing, I have shown my starter in schematicform connected into an operating circuit for a discharge lamp. Thedischarge lamp may comprise a fluorescent lamp I of a type now on themarket and which is provided at each end with electrodes 2 formed asfilamentary cathodes. On one side the electrodes are connected acrosspower lines 3 and 4 which, for example, may comprise a 115 volt A.-C.power supply such as is now commercially available for residence use.Connected into the power line 3 is a ballast 5 for supplyingv highvoltage to start the lamp. The ballast is illustrated as comprising aninductance or choke coil but it should be manifest that the ballast mayequally well comprise a transformer or resistance depending upon thevoltage requirements of the lamp and the voltage available at the powersupply. A switch 6 controls the application of power to the lampoperating circuit and is used to turn the lamp on and off.

While the discharge lamp I is illustrated as being provided withfilamentary electrodes, which may be used in a circuit providingpreheat, these electrodes are actually of the type which requirepractically no preheating before the application of the high voltagefrom the ballast to initiate a discharge in the lamp. In other words,the lamp is so constructed that it may be started simply by applying ahigh voltage across the electrodes without preheating them.

On the other side the electrodes are electrically connected in serieswith a control unit or starter constructed in accordance with myinvention. The. starter comprises a glow discharge device 7 electricallyconnected in series with a magnetically operated switch 8. A condenser 9is connected electrically in parallel across these elements. Thecapacity of the condenser affects the peak output voltage obtained bythe starter and also servesto reduce radio interference.

The glow discharge device 1 comprises a high current glow lamp havingtungsten electrodes of relatively large area so that the lamp is capableof carrying relatively heavy currents ordinarily sufficient to preheatthe lamp electrodes although in the instant circuit no appreciablepreheating of the filamentary lamp electrodes takes place. This currentmay be of the order of 300 to 600 milliamperes. The tungsten electrodesare sealed within a glass envelope in an atmosphere of a suitable inertgas such as neon, or the like. As shown by Fig. 1, one electrode of theglow lamp is connected by a lead wire In to the left-hand lamp electrode2 while the other electrode is connected by conductor H to the magneticswitch 8.

The switch or relay 8 comprises spaced contact members l2 such as silvercontact buttons which are normally closed by means of a contact bar l3carried by an iron armature I 4. The armature extends through a'solenoidcoil l5. One end of the coil is electrically connected in series withthe fixed contacts while the other end is connected by a lead wire 16 tothe other lamp electrode 2. The 'cont'actbar is normally biased intoengagement with the fixed contacts by a spring ll. The arrangement issuch that the circuit through the switch is normally closed. As soon asthe coil is energized the switch operates to open the'circuit throughthe starter. The contact bar. l3 and associated armature 'M are made ofrelatively light construction 'so'that'the 4 switch has a very fastaction upon being energized.

My starter operates as follows:

When switch 6 is closed to supply power to the lamp operating circuit,open circuit voltage is applied across the electrodes of the glow lamp ito initiate a .glow discharge. Immediately, a relatively heavy currentflows through the glow lamp to energize the switch 8. A circuit is thencompleted from power supply line 3 through ballast 5, the left-hand lampelectrode 2, glow lamp T, conductor li', switch contacts l2 and I3, coil15, the right-hand lamp electrode 2 to the other power line 4. As soonas voltage is applied to the magnetic switch 8, the normally closedcontacts of the switch are opened by the magnetic flux of the coil i5.

When the switch contacts open, the circuit through the starter isinterrupted so that a very high voltage kick is obtained .from theinductive ballast 5 and which is applied across the lamp electrodes.Frequently. one such surge of voltage is sufiicient to start the lampbut ordinarily the sequence of operation of the magnetic switch must berepeated two or three times before the lamp discharge is established.It'will be apparent that as soon as the switch contacts open, the coili5 will be deenergized permitting spring H to reclose the contacts. Inother words, as long as power is applied to the switch through the glowlamp the magnetic switch will vibrate to provide a series of impulses orvoltage kicks to the lamp l.

The series of voltage impulses are repeated i very rapidly so that theionization produced in the lamp by the first voltage impulse will bebuilt up and reinforced by the second impulse and also the third one andso on until the lamp lights. Stated technically, the starter is sodesigned that the periods of interruption of current, i. e., the periodsduring which the contacts of the magnetic switch are open to producehigh voltage impulses to the lamp, are shorter than the deionizationtime of the arc discharge in the lamp.

As already mentioned, the glow lamp passes a relatively heavy current onthe order of 300 to 600 milliamperes. This provides sufficient power for'fast and reliable operation of the magnetic switch. In addition, sincea relatively heavy current is passing through the inductive ballast amagnetic flux of considerable strength is built up so that when thecurrent is interrupted by operation of the starter an extremely highvoltage is developed by the ballast.

Condenser 9 functions to store part of the inductive energy obtainedfrom the ballast. The capacity of the. condenser may be varied somewhatto vary the peak output volts applied across the lamp filaments. Whenused with a 40 watt lamp and -115 volt A.-C. supply the condenser may beapproximately 0.2 mid. 'Its capacity is such that it serves to releasesome of the energy stored therein during the intervals betweensucceeding high voltage impulses. In this way, the condenser aids thestarting-action. In addition, the condenser acts to reduce radio noiseby absorbing the harmonic frequencies developed in the lamp arcdischarge.

As soon as the lamp lights, the voltage across the glow lamp 1 isreduced to that existing across the arc discharge in the lamp I. This isinsufficient to maintain the discharge in the glow lamp so that it nolonger passes current to energize switch 8. Thus the starter isimmediately cut out of the circuit. In this way, the glow lamp preventsany consumption of power in the starter mechanism while thelamp l islighted.

In the event that the lamp fails to light within the first fewvibrations of the magnetic switch, such as is ordinarily the case, theswitch will continue to operate in the manner indicated. However, it isnot desirable to permit the starter to operate for any appreciablelength of time. If the lamp is defective and fails to start afterseveral attempts have been made, I provide a mechanism for locking thestarter out of the lamp operating circuit.

Fig. 2 illustrates one form of lock-out mechanism which is suitable foruse in my starter. It comprises two bimetallic blades [8 and I9connected in series in the circuit between the magnetic switch 8 andconductor it. Each bimetallic blade carries a contact buttbn, thebuttons being normally in engagement with each other so that the circuitthrough the bimetallic blades is normally closed. A heating resistor 20is connected between the conductors l9 and IS in parallel with the glowlamp 7 and magnetic switch 8. If the lamp fails to start within a shorttime interval, the full line voltage existing across the lamp l andbetween conductors it and I6 causes the resistor to heat up to an extentsufficient to'cause bimetallic blade E9 to move U away from the bladeHi. This opens the circuit through the starter. It remains inopen-circuited condition as long as power is applied to the system andas long as the lamp fails to light. When power is turned 01 or when alamp is replaced thereby interrupting the circuit, the resistor coolsofi permitting the bimetallic members to reclose to reset the starter.Thus the starter is reset automatically. When the lamp lights, thevoltage applied to resistor 2!] is reduced so that the heat developed inthe resistor is insufiicient to move the bimetal 29. In such instancesthe starter is blocked out of the circuit by the glow lamp 1.

The lock-out mechanism has the advantage that, if the lamp is defective,the starter will not make attempts continuously to start the lamp. Suchrepeated starting attempts frequently cause the lamp to flash repeatedlyparticularly when the lamp is at the end of its rated life. Suchflashing is objectionable and is overcome by the lock-out mechanism.Since the starter is locked-out of the circuit after a number ofattempts to start the lamp, the starter itself is protected againstdamage and its life greatly increased. The resistor '26 consumes only asmall amount of power in maintaining the starter locked out. The twobimetallic members l8 and I9 are arranged to deflect in the samedirection when subjected to temperature changes. In this way thelock-out mechanism is compensated for changes in ambient temperature.

The starter is adapted for use in lamp operating circuits which aredesigned to give either cold cathode starting or preheat starting of thelamp. In other words, the starter may be used to give instant startingin existing lamp operating circuits equipped with preheat starterswithout rearranging the circuit connections and without replacing theballast or lamp sockets. It is only necessary to interchange thestarters. As already mentioned, the starter operates instantaneously toapply a very high voltage across the lamp electrodes without preheatingand in this way starts the lamp with the cathodes cold in a circuitoriginally designed for preheating. The starter mechanism can be usedinterchangeably with preheat starters in existing installationsemploying relatively low voltage ballasts, when an instant start lamp isemployed. It will operate equally as well on a D.-C. power source.

The glow lamp passes a relatively heavy current and the parts of theswitch 8 are made of relatively light construction so that an extremelyfast repetitive action of the switch is obtained. In spite of this fastaction, the starter stops operation instantly when the lamp lightsbecause the glow lamp will not pass current at the voltage existingacross a lighted lamp.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

A starter for discharge lamps comprising, in combination, a glowdischarge device adapted to pass current when subjected to apredetermined voltage and a magnetic switch having a series connectedcoil and normally closed contacts, said switch being electricallyconnected in series with said glow discharge device and being operableupon passage of a single impulse or repeated impulses of current throughthe device to interrupt the circuit through the starter.

2. A starter for discharge lamps comprising, in combination, a glow lampadapted to pass current when subjected to a predetermined voltage and amagnetically operated switch having a coil and normally closed contactselectrically connected together in series with said glow lamp and beingoperable by passage of each impulse of current through said glow lamp tointerrupt the circuit through said starter.

3. A starter for discharge lamps comprising, in combination, a glowdischarge device adapted to pass current upon application of apredetermined voltage, a magnetically operated switch having a coil andnormally closed contacts electrically connected together in series withsaid glow discharge device and being operable upon passage of a singleimpulse or repeated impulses r. of current through said device tointerrupt the circuit through said glow switch, and a capacitorelectrically connected in parallel with said glow discharge device andsaid magnetically operated switch.

4. A starter for electric discharge lamps comprising, in combination, aglow discharge device adapted to pass current when subjected to apredetermined voltage, a magnetic switch having a series connected coiland normally closed contacts, said switch bein electrically connected inseries with said glow discharge device and being operable upon passageof current through the device to interrupt the circuit through thestarter, and means electrically connected in circuit with said switchand being responsive to voltage across the lamp to interrupt the circuitthrough the starter in the event that the lamp fails to light.

5. A starter for use in an operating circuit for a discharge lampincluding a ballast and a source of power and adapted to be connectedbetween the lamp electrodes comprising, in combination, a glow dischargedevice, and a magnetic switch, said switch having normally closedcontacts and an operating coil therefor, said coil and contacts beingelectrically connected together in series with each other and with saidglow discharge device, said glow discharge device being operative uponapplication of power to energize said magnetic switch whereby themagnetic switch is operated to open the contacts to apply a high 7voltage from the ballast across the lamp electrodes to'start the lamp,.said'glow discharge device being inoperative upon starting of the lampto open' the circuit to said magnetic switch.

'6. A starter for an electric discharge lamp comprising, in combination,a voltage sensitive glow discharge device and a magnetic switch having aseries connected coil and normally closed contacts, said switch beingelectrically connected in series with said glow discharge device andbeing operable upon passage of a single impulse or repeated impulses ofcurrent through the device to interrupt the circuit through the starterfor :producing high voltage impulses for starting said lamp, the periodsduring which the contacts are 15 2 393, 32

open being shorter than the deionization time of the arc discharge insaid lamp.

LEONARD W. COOK.

REFERENCES CITED he following references are of record in the file ofthis patent:

UNITED STATES PATENTS 10 Number Name Date 2,212,427 Peters Aug. 20, 19402,270,368 Zecher Jan. 20, 1942 2,341,520 Babb Feb. 15, 1944 2,394,436Frech Feb. 5, 1946 Whiteside Apr. 16, 1946

